The field of the invention relates generally to nano-fabrication of structures. More particularly, the present invention is directed to a system that facilitates analysis of multiple patterns in superimposition suited for the manufacture of nano-scale devices.
Nano-scale fabrication involves the fabrication of very small structures, e.g., having features on the order of one nano-meter or more. A promising process for use in nano-scale fabrication is known as imprint lithography. Exemplary imprint lithography processes are described in detail in numerous publications, such as U.S. Patent Publication No. 2004-0065976 entitled “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensional Variability;” U.S. Patent Publication No. 2004-0065252 entitled “Method of Forming a Layer on a Substrate to Facilitate Fabrication of Metrology Standards;” and U.S. Pat. No. 6,936,194 entitled “Method and a Mold to Arrange Features on a Substrate to Replicate Features having Minimal Dimensions Variability;” all of which are assigned to the assignee of the present invention and are incorporated herein by reference.
Referring to FIG. 1, the basic concept behind imprint lithography is forming a relief pattern on a substrate that may function as, inter alia, an etching mask so that a pattern maybe formed into the substrate that corresponds to the relief pattern. A system employed to form the relief pattern includes a stage 10 upon which a substrate 12 is supported. A template 14, having a mold 16 with a patterning surface 18 thereon. Patterning surface 18 may be substantially smooth and/or planar or may be patterned so that one or more recesses are formed therein. Template 14 is coupled to an imprint head 20 to facilitate movement of template 14. A fluid dispense system 22 is coupled to be selectively placed in fluid communication with substrate 12 so as to deposit polymeric material 24 thereon. A source 26 of energy 28 is coupled to direct energy 28 along a path 30. Imprint head 20 and stage 10 are configured to arrange mold 16 and substrate 12, respectively, to be in superimposition and is disposed in path 30. Either imprint head 20, stage 10 or both vary a distance between mold 16 and substrate 12 to define a desired volume therebetween that is filled by polymeric material 24. Typically, polymeric material 24 is disposed upon substrate 12 before the desired volume is defined between mold 16 and substrate 12. However, polymeric material 24 may fill the volume after the desired volume has been obtained. After the desired volume is filled with polymeric material 24, source 26 produces energy 28, which causes polymeric material 24 to solidify and/or cross-link conforming to the shape of the substrate surface 24 and mold surface 18. Control of this process is regulated by processor 32 that is in data communication with stage 10 imprint head 20, fluid dispense system 22, source 26, operating on a computer readable program stored in memory 34.
To allow energy 28 to impinge upon polymeric material 24, it is desired that mold 16 be substantially transparent to the wavelength of energy 28 so that the same may propagate therethrough. Additionally, to maximize a flux of energy propagating through mold 16, energy has a sufficient cross-section to cover the entire area of mold 16 with no obstructions being present in path 30.
Referring to FIGS. 1 and 2 often a pattern generated by mold 16 is disposed upon a substrate 112 in which a preexisting pattern in present. To that end, a primer layer 36 is typically deposited upon patterned features, shown as recesses 38 and protrusions 40, formed into substrate 112 to provide a smooth, if not planar, surface 42 upon which to form a patterned imprint layer (not shown) from polymeric material 24 disposed upon surface 42. To that end, mold 16 and substrate 112 include alignment marks, which may include sub-portions of the patterned features. For example, mold 16 may have alignment marks, referred to as mold alignment marks, which are defined, by features 44 and 46. Substrate 112 may include alignment marks, referred to as substrate alignment marks, which are defined by features 48 and 50.
Not obtaining proper alignment between mold 16 and substrate 112 can introduce errors in that pattern recorded on substrate 112. In addition, to standard alignment errors, magnification/run out errors can creates distortions in the recorded pattern due, inter alia, to extenuative variations between mold 16 and region of substrate 112 to be patterned. The magnification/run-out errors occur when a region of substrate 112 in which the pattern on mold 16 is to be recorded exceeds the area of the pattern on mold 16. Additionally, magnification/run-out errors occur when the region of substrate 112 in which the pattern of mold 16 is to be recorded has an area smaller than the original pattern. The deleterious effects of magnification/run-out errors are exacerbated when forming multiple patterns in a common region. Additional errors may occur were the pattern on mold 16 rotated, along an axis normal to substrate 112, with respect to the region on substrate 112 in which the pattern on mold 16 is to be recorded. This is referred to as orientation error. Additionally, when the shape of the periphery of mold 16 differs from the shape of the perimeter of the region on substrate 112 on which the pattern is to be recorded also causes distortion. This typically occurs when transversely extending perimeter segments of either mold 16 and/or region of substrate 112 are not orthogonal. This is referred to as skew/orthogonality distortions.
To ensure proper alignment between the pattern on substrate 112 with the pattern generated by mold 16 it is desired to ensure proper alignment between the mold and substrate alignment marks. This has typically been achieved employing the aided eye, e.g., an alignment system 53 selectively placed in optical communication with both mold 16 and substrate 12, concurrently. Exemplary alignment systems have included ocular microscopes or other imaging systems. Alignment system 53 typically obtains information parallel to path 30. Alignment is then achieved manually by an operator or automatically using a vision system.
A need exists, therefore, to provide improved alignment techniques for imprint lithographic processes.